Ultra-high refractive index materials for patterning diffractive optical elements with nanoimprint lithography

Over the last two decades, the need for high-throughput and high-fidelity fabrication technology for micro and nano surface topologies designed for various photonic and optoelectronic devices has steadily driven the advancement of nanoimprint lithography technology (NIL). The availability of a functional high refractive index resin can enable high-volume and lowcost production of micro and nano-optical devices. However, available NIL-compatible resists have not kept up with the consumer industry's growing performance, processability, and reliability demands. In particular, for Augmented and Mixed Reality (AR and MR) devices, for the best optical performance (i.e., enhanced user experience) and reasonably low-cost production, a refractive index higher than 1.80 in the NIL resin is often desired. HighRI Optics, Inc. has developed two classes of materials with ultra-high refractive index, from 1.8 to 2.00 at 590 nm, for the nanoimprinting of photonic devices: 1) purely organic polymers and 2) nanocomposites consisting of polymeric matrix containing inorganic nanocrystals. The purely organic materials with a 1.8 refractive index do not contain nanoparticles, exhibit high transparency in the visible wavelength, and are NIL processable. The organic formulation has the highest refractive index ever reported among the organic polymers for nanoimprint lithography. The nanocomposites exhibit tunable refractive index values between 1.8 ~ 2.0 at 590 nm, with high optical transparency and low haze. These materials can become an essential part of the ecosystem to enable the mass production of future photonic devices.